Alexander Bain was a Scottish philosopher who influenced the Americans Charles Sanders Peirce and William James. Their meetings of the short-lived "Metaphysical Club" in the early 1860's often included discussions of Bain's work. Peirce thought the core idea of his new philosophy of pragmatism came from Bain's definition of a belief as "that upon which a man is prepared to act."

William James gave "The Will to Believe" agential force in his own version of pragmatism. The "difference between the objects of will and belief is entirely immaterial, as far as the relation of the mind to them goes." (Principles, vol.2, p.320) "When a thing is such as to make us act on it, then we believe it, according to Bain," said James (p.322).

In his 1859 book Emotions and the Will, Bain said

It remains to consider the line of demarcation between belief and mere conceptions involving no belief - there being instances where the one seems to shade into the other. It seems to me impossible to draw this line without referring to action, as the only test, and the essential import of the state of conviction even in cases the farthest removed in appearance from any actions of ours, there is no other criterion.

Bain followed John Locke and considered it absurd to describe the will as "free." His psychological theory marked the beginning of psychophysical parallelism, and it denied a purely physical or materialist explanation of mind. Knowledge and all mental events flowed from the sensations. So the physical body could generate spontaneous movements, but they could be known to a Laplacian intelligence.

Spontaneity, Self determination. - These names are introduced into the discussion of the will, as aides to the theory of liberty, which they are supposed to elucidate and unfold. That there is such a thing as 'spontaneity,' in the action of voluntary agents has been seen in the foregoing pages. The spontaneous beginnings of movement are a result of the physical mechanism under the stimulus of nutrition... There is nothing in all this that either takes human actions out of the sweep of law, or renders liberty and necessity appropriate terms of description... The physical, or nutritive, stimulus is a fact of our Constitution, counting at each moment for a certain amount, according to the bodily condition; and if anyone knew exactly the condition of a man or animal in this respect, a correct allowance might be made in the computation of present motives.

Bain thought that the mind also could generate "outgoing" thoughts and new associations at "random," but it is likely that his idea of randomness was the prevalent 19th-century view that randomness and chance were just the result of human ignorance and our incapacity to make arbitrarily accurate measurements, following the views of Adolphe Quételet and Henry Thomas Buckle.

When Watt invented his 'parallel motion' for the steam engine, his intellect and observation were kept at work, going out in all directions for the change of some suitable combination rising to view; his sense of the precise thing to be done was the constant touchstone of every contrivance occurring to him, and all the successive suggestions were arrested, or repelled, as they came near to, or disagreed with, this touchstone. The attraction and repulsion were purely volitional effects; they were the continuance of the very same energy that, in his babyhood, made him keep his mouth to his mother's breast widely felt hunger on appeased and withdraw it when satisfied...

No formal resolution of the mind, adopted after consideration or debate, no special intervention of the 'ego,' or the personality, is essential to this putting forth of the energy of retaining on the one hand, or repudiating on the other, what is felt to be clearly suitable, or clearly unsuitable, to the feelings or aims of the moment. The inventor sees the incongruity of a proposal, and forth with it vanishes from his view. There may be extraneous considerations happening to keep it up in spite of the volitional stroke of repudiation, but the genuine tendency of the mind is to withdraw all further consideration, on the mere motive of unsuitability; while some other scheme of an opposite nature is, by the same instinct, embraced and held fast.

In all these new constructions, be they mechanical, verbal, scientific, practical, or aesthetical, the outgoings of the mind are necessarily at random; the end alone is the thing that is clear to the view, and with that there is a perception of the fitness of every passing suggestion. The volitional energy keeps up the attention, or the active search, and the moment that anything in point rises before the mind, springs upon that like a wild beast on its prey. I might go through all the varieties of creative effort, detailed under the law of constructive association, but I should only have to repeat the same observation at every turn.

(Emotions and the Will, ch. IV, Control of Feeling and Thoughts, sect. 8, Constructive Association a Voluntary Process, p.413-4)

Among Bain's many accomplishments was the founding of the influential philosophical journal, Mind, in 1876.